Ger. Pat. 3,920,342 discloses a method of decontaminating a contaminated soil region wherein a contaminant which is electrokinetically transportable and is contained in a soil region which contains an electrically conducting liquid is collected electrophoretically at at least one predetermined location of the soil region. For this purpose, a well is sunk in the soil region, wherewith the well tubing extends through the aquifer layer. An underpressure is applied to this well, whereby the soil gases contained in the soil, along with the harmful substance[s] therein, are removed by suction. In the middle of the well a lance-shaped central cathode is disposed which extends through the aquifer layer and the non-aquifer layer thereabove. At a small distance from the well, e.g. 6 m, a plurality of lance-chaped anodes are disposed. By applying a voltage between the anodes and the central cathode, an electric field directed radially toward the cathode is produced in the aquifer layer and the non-aquifer layer thereabove. The electric current produced in the aquifer layer, and the non-aquifer layer thereabove, by the applied voltage, causes ions of the harmful substance[s] to be produced by thermal ionization and to migrate toward the well. The known method is used exclusively in connection with electrokinetically transportable harmful substances.
The underlying problem of the present invention is to devise a method and apparatus for electrochemical removal of harmful substances, particularly in the earth's surface, whereby harmful substances can be removed, particularly in the earth's surface, in place (in situ), without local displacement or excavation.